Air travel and the end of oil

While eating vegetarian Pho the other day, I had an idea relevant to our running series of discussions on air travel. Specifically, this: if we are basically certain to consume all the world’s accessible oil eventually and, if the long atmospheric life of carbon dioxide means that it matters little whether emissions occur in one year or another, might it not be sensible to fly about without guilt. After all, the atmosphere is doomed to absorb all the CO2 from oil anyhow. You could compare it to keeping warm beside a fire you didn’t start, and which is naturally going to carry on burning until there is no fuel left.

For a brief moment, this seemed like a good justification. Unfortunately, it suffers from at least two critical problems.

Timing matters

Firstly, it inappropriately downplays the importance of timing. This is true both environmentally and economically. Environmentally, we might compare CO2 emissions from oil to drinking vodka at a party. You have the option of taking one shot an hour, until the bottle is gone, or guzzling it all in a few minutes. In theory, both approaches produce a similar amount of intoxication. In one case, it is just bunched up at the beginning. The trouble lies with non-linear responses to such external forcings. Your liver and kidneys can probably handle one shot an hour. They may well be unable to handle twenty shots an hour. They might fail, and you might die. Something similar could be true of the climate system. It might be possible to avoid catastrophic tipping points if emissions rise and then fall back in a long smooth arc. It’s not an ideal option (global emissions should already be falling, if we really want to avoid catastrophe), but it is a safer option than guzzling.

Economically, it also makes sense to portion out our remaining fuel. Essentially, that is because we need to make a transition to a low-oil, low-carbon global economy. In the future, oil will be used in fewer ways and will be used more efficiently in all of them. To take an example, it would seem like folly to burn gasoline to travel 10km to work. Because oil will be both more costly and more efficiently used in the future, it is essentially worth more there and should be saved. There are also areas in which ready replacements for oil do not exist: air travel being a critical one. Saving our oil for the future cases where nothing else will do makes sense.

Worse stuff than petroleum

Secondly, there is the enormous problem of fuel substitution. Kerosene made from petroleum is a high-emission option, but nowhere near the worst option out there. Fuels made from oil sands or (shudder) shale oil could be much more emissions intensive. The same is true of palm oil – a biofuel largely grown in areas of former rainforest. Finally, there is the danger that the coal-to-liquids technology used in oil-starved WWII Germany and Japan could become widespread. Eventually, it is likely that at least some commercial jet fuel (and perhaps more military jet fuel) will come from such horrid sources. That is a big problem.

While there is some chance we can burn all the world’s oil without wrecking the climate, that is enormously less likely if we are going to burn all the coal as well. Avoiding the switch to suicide fuels is a critical task, and one that can be aided by limiting air travel.

Another problem, is that Co2 is not the only problem with flying – there seems to be a serious possibility that particulate emissions and water emisions from planes has a significant effect on the atmosphere. If “global darkening” isn’t just hogwash, then we need to worry about the extent to which we are already geo-engineering the atmosphere, mitigating global warming.

And if you wish to torque up your angst a bit more yet, may I suggest asking where the veggies in that pho came from?

Chances are reasonable that they were grown and processed in China. It amazes me that an Ottawa grocery store can sell, for about two bucks, a half-kilo blend of baby corn, snow peas and peppers that are grown, harvested, presteamed, frozen and packaged in plastic microwavable pouches in China, then shipped here in refrigerated containers. Whenever I see them in the freezer section, I have to wonder what the carbon footprint of each pea pod might be…

There is no DANGER that fuels will come from coal-to-liquids.
That is a huge solution, because those fuels are absolutely clean.
The CO2 can be caught and sequestered, and through the use of a mix of bio material in the feed, the process will produce less CO2 well-to-wheels than current fuels.
You should wholeheartedly support it, and not parrot the misrepresentation of current press.
Do some independent research before killing the only thing that can save our society.

First, making liquid fuels from coal produces emissions. You are right to say that it is theoretically possible to sequester these, but CCS has never been commercially deployed at a large scale. Furthermore, CCS equipment will take extra energy to run.

Secondly, the liquid fuel you make from coal will still produce CO2, and it is impossible to use CCS on an airplane.

“Half of the work done by a plane goes into staying up; the other half goes into keeping going. The fuel efficiency at the optimal speed, expressed as an energy-per-distance-travelled, was found in the force (C.18), and it was simply proportional to the weight of the plane; the constant of proportionality is the drag-to-lift ratio, which is determined by the shape of the plane. So whereas lowering speed-limits for cars would reduce the energy consumed per distance travelled, there is no point in considering speedlimits for planes. Planes that are up in the air have optimal speeds, different for each plane, depending on its weight, and they already go at their optimal speeds. The only way to make a plane consume less fuel is to put it on the ground and stop it. Planes have been fantastically optimized, and there is no prospect of significant improvements in plane efficiency.”

…

“Possible areas for improvement of plane efficiency

‘Laminar flow control’ (cunning trick for reducing drag a little). Flying wings: said to be 25% more fuel efficient. Propfans instead of turbofans? Said to be 12% more efficient for short journeys (less than 3000 km), but not for long journeys. They’re more efficient because the engine efficiency is greater.

Formation flying in the style of geese could give a 10% improvement in fuel efficiency (because the lift-to-drag ratio of the formation is higher than that of a single aircraft), but this trick relies, of course, on the geese wanting to migrate to the same destination at the same time.

Optimizing the hop lengths: long-range planes (designed for a range of say 15 000 km) are not quite as fuel-efficient as shorter-range planes, because they have to carry extra fuel, which makes less space for cargo and passengers. It would be more energy efficient to fly shorter hops in shorter-range planes. The sweet spot is when the hops are about 5000 km long, so typical long-distance journeys would have one or two refuelling stops. Multi-stage long distance flying might be abou”

…

“Earlier in this chapter, however, our cartoon made the assertion that the transport efficiency of any plane is about

0.3 kWh/tonne-km.

According to the cartoon, the only ways in which a plane could significantly improve on this figure are to reduce air resistance (perhaps by some newfangled vacuum-cleaners-in-the-wings trick) or to change the geometry of the plane (making it look more like a glider, with immensely wide wings compared.”

Q: There has been quite a lot of work done on using bio-fuels to power aircraft. All three major engine manufacturers have recently had successful flight trials. The suggestion is that these can be produced by either algae or jatropha. Given the willingness of aviation to pay a relatively high price for its fuel, is this unrealistic?